The present invention belongs to the technical field of a magnetic tape used for the record and reproduction of information. More particularly, the present invention relates to magnetic tape processing method and apparatus capable of effectively manufacturing a magnetic tape in such a manner that even if the magnetic tape is transported at a high speed in the manufacturing process and the like thereof, no slip is caused to the magnetic tape and thus the damage of the magnetic tape and the disturbance of the wound appearance thereof due to the slip can be prevented and further cupping is also reduced.
Magnetic tapes used to record and reproduce information are basically composed of a base layer which is a film such as PET (polyethylene terephthalate) and the like, a magnetic layer formed on one of the surfaces of the base layer, a backing layer formed on the surface of the base layer opposite to the magnetic layer for the purpose of improving the stability of the magnetic tape when it is transported and the strength thereof, and the like.
In the manufacturing process of the magnetic tapes, a magnetic tape (hereinafter, referred to as tape) is subjected to various types of processing such as the cutting of the tape with a slitter, the cleaning of the surface thereof with a blade edge while it is transported in the lengthwise direction thereof, made to a pancake or a cassette by being wound around a hub and delivered to the next process or to a customer. Incidentally, there is recently a tendency that tapes are transported at a high speed (transportation speed is increased), in various types of processes (manufacturing apparatus such as a blade machine, a winder and the like) for the enhancement of productivity.
The transportation of a tape is carried out by wrapping it on a capstan roller and rotating the capstan roller.
However, when the transportation speed of the tape is increased, the tape entraines air in the manufacturing apparatus such as the blade machine, slitter and the like and floats above the capstan roller and the like, whereby the tape slips and may no be normally transported.
As a result, the tape collides against or comes into improper contact with the capstan roller, a guide roller, the blade edge and the like, whereby the damage of the tape is caused such as the breakage of the tape itself or the edge thereof, the wear and peeling of the magnetic layer, and the like. Thus, a resulting tape is made improper as a product. Further, a roller for measuring a tape length (length detecting roller) is mounted on the tape manufacturing apparatus when necessary. However, when the tape slips on the length detecting roller, an error arises in the measurement of the tape length and thus a problem also arises in that the production of the tape cannot be properly managed.
Accordingly, it is difficult to increase the tape transportation speed in correspondence to the required improvement of a manufacturing efficiency in the manufacture of tape.
Further, cupping is known as another problem of magnetic tapes. Cupping is the curl of a magnetic tape in the width direction thereof and mainly caused by the difference of shrinking ratios between respective binders used in a magnetic layer and a backing layer.
Various problems are caused by the occurrence of the cupping such as the deterioration of the outside appearance of a magnetic tape as a product; the possibility of the occurrence of recording error and reading error due to the deteriorated touch of the magnetic tape against a recording head and a reading head; the lowered durability of the magnetic tape because the edges thereof are liable to be damaged, and the like.
The cupping can be improved by the methods of increasing the thickness of a magnetic layer, reducing the thickness of a backing layer, adjusting the prescription of the magnetic layer and the backing layer, and the like. However, the improvement of the cupping is limited by various kinds of problems in manufacturing process, prescription, performance capability, and the like.
More specifically, recently, the recording density of a magnetic tape has been improved. To realize the improvement, the thickness of the magnetic layer tends to be reduced. When the thickness of the backing layer is reduced accordingly for the purpose of preventing cupping, the strength of the magnetic tape is lowered and a problem arises in the durability of the tape when it is in practical use. Further, when the prescription of the magnetic layer and the backing layer is changed, the characteristics of the magnetic tape are changed and there is a possibility that a target performance capability cannot be obtained.
That is, it is a very time-consuming job to reduce the cupping by adjusting the prescription of the magnetic layer, the backing layer and the like while preventing the deterioration of the performance capability. Thus, this job is very disadvantage in the efficiency of development, the cost of the magnetic tape, and the like.
A first object of the present invention is to solve the problems of the conventional technology and to provide a magnetic tape processing method and apparatus which can efficiently manufacture a magnetic tape having excellent characteristics such that the occurrence of the slip of the magnetic tape is not caused on a capstan roller and the like, even if the transportation speed of the tape is increased in a magnetic tape manufacturing apparatus, and furthermore a size of cupping of the magnetic tape is small.
The second object of the present invention is to provide a magnetic tape processing apparatus which can manufacture efficiently the magnetic tape having the excellent characteristics described above and carry out the magnetic tape processing method described above.
The use of the magnetic tape processed by the present invention permits the magnetic tape to be precisely transported at a high speed in the magnetic tape manufacturing apparatus such as a blade machine, a winder and the like. Accordingly, a magnetic tape without damage can be stably manufactured with a high manufacturing efficiency under proper production management and further when the magnetic tape is wound and made to a winder and a pancake, the wound appearance of the magnetic tape can be made beautiful. Furthermore, the deteriorated outside appearance of the magnetic tape, the deteriorated abutment of the magnetic tape against a head, the damage of the edges of the magnetic tape, and the like due to the cupping can be also prevented.
To achieve the first object described above, the present invention provides a magnetic tape processing method characterized by comprising the steps of allowing at least one of a laser beam or laser beams in a visible region and a laser beam or laser beams in an ultraviolet region to be incident on a backing layer of a magnetic tape while transporting the magnetic tape in a lengthwise direction of the magnetic tape; and processing the backing layer by means of the laser beam or laser beams to form recesses on the backing layer.
In the magnetic tape manufacturing method of the present invention, it is preferable that the laser beam or laser beams incident on the backing layer of the magnetic tape is at least one of a plurality of laser beams which are divided and imaged by a multiple-lens, a plurality of laser beams divided by a divider and a laser beam scanned by at least one light scanning element, it is preferable that the multiple-lens is arranged such that lenses disposed in at least one of a densest state, a grid state, and one row and a plurality rows in a direction having an angle with respect to the lengthwise direction, is preferable that processing intensity of an recess formed on the backing layer is increased by forming the recess with a plurality of laser beams by overlapping optical axes of the lenses in the lengthwise direction, it is preferable that at least one of reciprocating motion of the magnetic tape in a direction perpendicular to a transporting direction of the magnetic tape, reciprocating motion of the laser beam or laser beams in the direction perpendicular to the transporting direction of the magnetic tape, and adjustment of intervals at which the recesses are formed is carried out while the backing layer is being processed, and further it is preferable that the laser beam or laser beams is at least one of a laser beam of 488 nm and a laser beam of 515 nm emitted from argon lasers and a laser beam of 532 nm obtained by subjecting a YAG laser to wavelength conversion with a second harmonic generation element.
Further, to achieve the second object described above, the present invention provides a magnetic tape processing apparatus characterized by comprising at least one light source for emitting at least one laser beam in at least one of a visible region and an ultraviolet region; an optical system for applying the at least one laser beam emitted from the at least one light source to a predetermined processing position or positions; a transportation device for transporting a magnetic tape in a lengthwise direction of the magnetic tape at the predetermined processing position or positions in a state that a backing layer of the magnetic tape faces upper stream of at least one light path of the at least one laser beam; and a device for securing the flatness of the magnetic tape transported by the transportation device at the predetermined processing position of positions.
In the magnetic tape processing apparatus of the present invention, it is preferably that the optical system includes a beam expander and a multiple-lens, it is preferable that the multiple-lens is arranged such that lenses disposed in at least one of a densest state, a grid state, and one row and a plurality rows in a direction having an angle with respect to the lengthwise direction, it is preferable that processing intensity of an recess formed on the backing layer is increased by forming the recess with a plurality of laser beams by overlapping optical axes of the lenses in the lengthwise direction, it is preferable that the optical system includes a beam waist position adjustment device, a laser beam divider and a converging lens, it is preferable that the at least one light source is composed of a semiconductor laser array and the optical system includes an imaging device for imaging laser beams emitted from the semiconductor laser array, it is preferable that the optical system includes a light deflecting element for scanning at least one laser beam at an angle with respect to a transporting direction of the magnetic tape transported by the transportation device and a scanning lens, it is preferable that the magnetic tape processing apparatus further comprises at least one of a device for reciprocating the magnetic tape in a direction perpendicular to a transporting direction of the magnetic tape at the predetermined processing position or positions, device for reciprocating the laser beams in a direction perpendicular to the transporting direction of the magnetic tape at the predetermined processing position or positions, and a device for adjusting the intervals at which the laser beams are irradiated to the magnetic tape, it is preferable that the at least one light source is at least one of an argon laser of 488 nm, an argon laser of 515 nm and a wavelength conversion laser for emitting a laser beam of 532 nm which is obtained by subjecting a YAG laser to wavelength conversion with a second harmonic generation element, it is preferable that the transportation device comprises a transportation drive device including a capstan roller, a rewinder and a winder, and at least one guide roller, and wherein the securing device is a tape flatener, it is preferable that the tape flatener is touched against a surface of a magnetic layer side of the magnetic tape being transported and positions the magnetic tape at the predetermined processing position or positions, it is preferable that the at least one guide roller is two guide rollers are disposed in the lengthwise direction across the tape flatener, wherein a transportation passage of the magnetic tape formed by the two guide rollers is below a transportation passage of the magnetic tape formed by the tape flatener and wherein the magnetic tape is positioned at the processing position or positions by being pressed against the tape flatener and supported on the tape flatener, it is preferable that the tape flatener is at least one of at least two triangular prisms, a plurality of support members as semi-circular columns, a plurality of support members as columns and a plate type flatener, it is preferable that the laser beam reciprocating device is at least one of a piezo-electric element and a voice coil which move a multiple-lens of the optical system, it is preferable that wave-shaped recesses on the backing layer of the magnetic tape are formed by reciprocating the laser beams with the laser beam reciprocating device such that the wave-shaped recesses are not overlapped on at least upper and lower turns of the magnetic tape when the magnetic tape is wound, it is preferable that the laser beam reciprocating device is arranged the light source and the optical system as a unit and reciprocates the unit.
Further the present invention provides a magnetic tape processing apparatus characterized by comprising a hollow cylindrical drum being rotatable about an axial line thereof and provided with light passing portions and shading portions which are formed in a predetermined pattern along a cylindrical wall thereof; at least one light source for emitting at least one laser beam; an optical system for making to a sheet-shaped laser light and then introducing the sheet-shaped laser light in a hollow portion of the hollow cylindrical drum to apply the sheet-shaped laser light to a row of the light passing portions of the hollow cylindrical drum from inside to outside; and a transportation device for transporting a magnetic tape in a lengthwise direction thereof in contact with or in no contact with a circumferential surface of the hollow cylindrical drum, wherein the hollow cylindrical drum is rotated synchronously with the magnetic tape transported by the transportation device so that a row of divided laser beams passing through the row of light passing portions are incident on a backing layer of the magnetic tape to from recesses on the backing layer.
In the magnetic tape processing apparatus, it is preferable that the magnetic tape processing apparatus further comprises a rotating drive source for rotating the hollow cylindrical drum synchronously with the magnetic tape transported by the transportation device, it is preferable that the hollow cylindrical drum is a cylindrical tape guide having a multiplicity of apertures passing through a side wall and being rotatable about an axial line thereof, wherein the optical system comprises a sheet light forming device for making a sheet-shaped laser light and applying it to a interior of the cylindrical tape guide downwardly; and a mirror fixed in the interior of the cylindrical tape guide at an angle of 45xc2x0 with its reflecting surface facing upward, the mirror bending the sheet-shaped laser light at an angle of 90xc2x0 and applying it to an inner surface of the cylindrical tape guide so as to draw a line on the inner surface thereof, and wherein the cylindrical tape guide is rotated synchronously with the magnetic tape transported in contact with or in no contact with an outer surface of the cylindrical tape guide so that a multiplicity of divided laser beams passing through the multiplicity of the apertures are incident on a backing layer of the magnetic tape to form recesses on the backing layer, it is preferable that the apertures extends in an axial direction of the cylindrical tape guide, it is preferable that the line drawn by the sheet-shaped laser light extends in an axial direction of the cylindrical tape guide or a direction oblique to the axial direction, other line is a line drawn by the sheet-shaped laser light incident on a predetermined position of the inner surface of the cylindrical tape guide, it is preferable that the magnetic tape processing apparatus further comprises a guide cleaner for cleaning the outer surface of the cylindrical tape guide and being touched against the outer surface thereof, it is preferable that the apertures are one of through holes formed as the light passing portions in a shading cylinder and the light passing portions of a mask pattern having the light passing portions and the shading portions which is formed on a transparent cylinder, and wherein each of the shading cylinder having the through holes and the transparent cylinder having the mask pattern is the cylindrical tape guide, it is preferable that the through holes are formed by applying a YAG laser to the shading cylinder made of metal, and wherein the mask pattern is formed on the transparent cylinder composed of quartz glass using one of a vapor-deposited thin film by vapor deposition of metal, film transfer and print, it is preferable that the optical system further comprises small lenses disposed to the apertures and imaged the divided laser beams passing through the apertures on the backing layer of the of the magnetic tape through the small lenses, and further it is preferable that the small lenses are bead glasses, microball lenses, gradient index lenses of micro-mold lenses.